Fluids are conveyed through pipes and conduits for all sorts of purposes: heating systems, hydraulic systems, fluid transport, water supply systems, refrigeration systems, and similar purposes. In such systems many types of valves are used for servicing or control. Valve types include shut-off valves, check valves, throttling valves, relief valves, pressure regulating valves, solenoid valves, and, among others, motorized valves powered by air, hydraulics, or electricity.
Motorized valves are useable for most types of fluids including refrigerants, brines, water, oils hydraulic liquids, and similar fluids. As systems have become more complicated and requirements more precision, there has been an increasing need for a broader range of motorized valves along with the other related more simple valves mentioned above. However, as environmental atmospheric pollution requirements become increasingly stringent, there is an increasing need to eliminate valve designs with external motors having valve stems and accompanying stem packings. This has caused a trend toward valve concepts having internal motors or motors whose forces are transmitted to the valve seat via magnetic rotary couplings or other leak proof stationary barrier designs instead of stems and packings. Internal motors having electrical parts in the controlled fluid suffer from corrosion or high friction problems while magnetic couplings have high friction and reliability concerns.